JEE Advanced 2025 — Paper 1 — CHEM-IV solution

JEE Advanced2025Paper 1CHEM-IV

The correct match of the group reagents in List-I for precipitating the metal ion given in List-II from solutions, is

List-I	List-II
(P) Passing H $_{2}$ S in the presence of NH $_{4}$ OH	(1) Cu $^{2 +}$
(Q) (NH $_{4}$ ) $_{2}$ CO $_{3}$ in the presence of NH $_{4}$ OH	(2) Al $^{3 +}$
(R) NH $_{4}$ OH in the presence of NH $_{4}$ Cl	(3) Mn $^{2 +}$
(S) Passing H $_{2}$ S in the presence of dilute HCl	(4) Ba $^{2 +}$
	(5) Mg $^{2 +}$

A
P $\to$ 3; Q $\to$ 4; R $\to$ 2; S $\to$ 1
B
P $\to$ 4; Q $\to$ 2; R $\to$ 3; S $\to$ 1
C
P $\to$ 3; Q $\to$ 4; R $\to$ 1; S $\to$ 5
D
P $\to$ 5; Q $\to$ 3; R $\to$ 2; S $\to$ 4

Solution

Classical group analysis classifies cations by the reagent that selectively precipitates them.

(P) H $_{2}$ S in the presence of NH $_{4}$ OH (alkaline H $_{2}$ S) precipitates Group IV sulfides. Mn $^{2 +}$ gives the characteristic pink-buff MnS. Matches (3).

(Q) (NH $_{4}$ ) $_{2}$ CO $_{3}$ with NH $_{4}$ OH (Group V carbonate reagent) precipitates Ba $^{2 +}$ as white BaCO $_{3}$ . Matches (4).

(R) NH $_{4}$ OH with NH $_{4}$ Cl (Group III reagent at low [OH $^{-}$ ]) precipitates Al $^{3 +}$ as gelatinous white Al(OH) $_{3}$ . Matches (2).

(S) H $_{2}$ S in dilute HCl (Group II reagent) precipitates Cu $^{2 +}$ as black CuS. Matches (1).

$∴$ P $\to$ 3, Q $\to$ 4, R $\to$ 2, S $\to$ 1. Option (A).

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